C# where语句查询时的多参数Func

适用场景：查询条件为有限个且动态的，查询条件有值时考虑，无值时不考虑。
gitee地址：https://gitee.com/zhangyf6548/winfrom-scaffold
首先winform界面方便调试

namespace WinFormsApp1
{
    partial class LandDataForm
    {
        /// <summary>
        /// Required designer variable.
        /// </summary>
        private System.ComponentModel.IContainer components = null;

        /// <summary>
        /// Clean up any resources being used.
        /// </summary>
        /// <param name="disposing">true if managed resources should be disposed; otherwise, false.</param>
        protected override void Dispose(bool disposing)
        {
            if (disposing && (components != null))
            {
                components.Dispose();
            }
            base.Dispose(disposing);
        }

        #region Windows Form Designer generated code

        /// <summary>
        /// Required method for Designer support - do not modify
        /// the contents of this method with the code editor.
        /// </summary>
        private void InitializeComponent()
        {
            System.Windows.Forms.DataGridViewCellStyle dataGridViewCellStyle1 = new System.Windows.Forms.DataGridViewCellStyle();
            this.label1 = new System.Windows.Forms.Label();
            this.btn_Ok = new System.Windows.Forms.Button();
            this.btn_Cancel = new System.Windows.Forms.Button();
            this.openFileDialog1 = new System.Windows.Forms.OpenFileDialog();
            this.dataGridView1 = new System.Windows.Forms.DataGridView();
            this.Column1 = new System.Windows.Forms.DataGridViewTextBoxColumn();
            this.Column4 = new System.Windows.Forms.DataGridViewTextBoxColumn();
            this.Column2 = new System.Windows.Forms.DataGridViewTextBoxColumn();
            this.Column3 = new System.Windows.Forms.DataGridViewTextBoxColumn();
            this.label2 = new System.Windows.Forms.Label();
            this.label3 = new System.Windows.Forms.Label();
            this.btnQuery = new System.Windows.Forms.Button();
            this.txtNum = new System.Windows.Forms.TextBox();
            this.txtName = new System.Windows.Forms.TextBox();
            this.txtLocation = new System.Windows.Forms.TextBox();
            ((System.ComponentModel.ISupportInitialize)(this.dataGridView1)).BeginInit();
            this.SuspendLayout();
            // 
            // label1
            // 
            this.label1.AutoSize = true;
            this.label1.Location = new System.Drawing.Point(26, 15);
            this.label1.Margin = new System.Windows.Forms.Padding(2, 0, 2, 0);
            this.label1.Name = "label1";
            this.label1.Size = new System.Drawing.Size(54, 20);
            this.label1.TabIndex = 0;
            this.label1.Text = "编号：";
            // 
            // btn_Ok
            // 
            this.btn_Ok.Location = new System.Drawing.Point(351, 487);
            this.btn_Ok.Margin = new System.Windows.Forms.Padding(2, 4, 2, 4);
            this.btn_Ok.Name = "btn_Ok";
            this.btn_Ok.Size = new System.Drawing.Size(96, 31);
            this.btn_Ok.TabIndex = 5;
            this.btn_Ok.Text = "确定";
            this.btn_Ok.UseVisualStyleBackColor = true;
            this.btn_Ok.Click += new System.EventHandler(this.btn_Ok_Click);
            // 
            // btn_Cancel
            // 
            this.btn_Cancel.Location = new System.Drawing.Point(486, 487);
            this.btn_Cancel.Margin = new System.Windows.Forms.Padding(2, 4, 2, 4);
            this.btn_Cancel.Name = "btn_Cancel";
            this.btn_Cancel.Size = new System.Drawing.Size(96, 31);
            this.btn_Cancel.TabIndex = 6;
            this.btn_Cancel.Text = "取消";
            this.btn_Cancel.UseVisualStyleBackColor = true;
            this.btn_Cancel.Click += new System.EventHandler(this.btn_Cancel_Click);
            // 
            // openFileDialog1
            // 
            this.openFileDialog1.FileName = "openFileDialog1";
            // 
            // dataGridView1
            // 
            this.dataGridView1.AllowUserToAddRows = false;
            this.dataGridView1.AllowUserToDeleteRows = false;
            this.dataGridView1.AllowUserToResizeColumns = false;
            this.dataGridView1.AllowUserToResizeRows = false;
            this.dataGridView1.BackgroundColor = System.Drawing.Color.White;
            this.dataGridView1.BorderStyle = System.Windows.Forms.BorderStyle.None;
            dataGridViewCellStyle1.Alignment = System.Windows.Forms.DataGridViewContentAlignment.MiddleCenter;
            dataGridViewCellStyle1.BackColor = System.Drawing.SystemColors.Control;
            dataGridViewCellStyle1.Font = new System.Drawing.Font("微软雅黑", 9F, System.Drawing.FontStyle.Regular, System.Drawing.GraphicsUnit.Point);
            dataGridViewCellStyle1.ForeColor = System.Drawing.SystemColors.WindowText;
            dataGridViewCellStyle1.SelectionBackColor = System.Drawing.SystemColors.Highlight;
            dataGridViewCellStyle1.SelectionForeColor = System.Drawing.SystemColors.HighlightText;
            dataGridViewCellStyle1.WrapMode = System.Windows.Forms.DataGridViewTriState.True;
            this.dataGridView1.ColumnHeadersDefaultCellStyle = dataGridViewCellStyle1;
            this.dataGridView1.ColumnHeadersHeight = 29;
            this.dataGridView1.ColumnHeadersHeightSizeMode = System.Windows.Forms.DataGridViewColumnHeadersHeightSizeMode.DisableResizing;
            this.dataGridView1.Columns.AddRange(new System.Windows.Forms.DataGridViewColumn[] {
            this.Column1,
            this.Column4,
            this.Column2,
            this.Column3});
            this.dataGridView1.Location = new System.Drawing.Point(30, 58);
            this.dataGridView1.Margin = new System.Windows.Forms.Padding(2, 4, 2, 4);
            this.dataGridView1.Name = "dataGridView1";
            this.dataGridView1.RowHeadersVisible = false;
            this.dataGridView1.RowHeadersWidth = 51;
            this.dataGridView1.RowTemplate.Height = 27;
            this.dataGridView1.Size = new System.Drawing.Size(876, 383);
            this.dataGridView1.TabIndex = 8;
            this.dataGridView1.RowPostPaint += new System.Windows.Forms.DataGridViewRowPostPaintEventHandler(this.dataGridView1_RowPostPaint);
            // 
            // Column1
            // 
            this.Column1.DataPropertyName = "index";
            this.Column1.HeaderText = "序号";
            this.Column1.MinimumWidth = 6;
            this.Column1.Name = "Column1";
            this.Column1.Resizable = System.Windows.Forms.DataGridViewTriState.True;
            this.Column1.SortMode = System.Windows.Forms.DataGridViewColumnSortMode.NotSortable;
            this.Column1.Width = 125;
            // 
            // Column4
            // 
            this.Column4.DataPropertyName = "num";
            this.Column4.HeaderText = "编号";
            this.Column4.MinimumWidth = 6;
            this.Column4.Name = "Column4";
            this.Column4.Width = 190;
            // 
            // Column2
            // 
            this.Column2.DataPropertyName = "name";
            this.Column2.HeaderText = "名称";
            this.Column2.MinimumWidth = 6;
            this.Column2.Name = "Column2";
            this.Column2.Width = 200;
            // 
            // Column3
            // 
            this.Column3.DataPropertyName = "location";
            this.Column3.HeaderText = "位置";
            this.Column3.MinimumWidth = 6;
            this.Column3.Name = "Column3";
            this.Column3.Width = 300;
            // 
            // label2
            // 
            this.label2.AutoSize = true;
            this.label2.Location = new System.Drawing.Point(208, 15);
            this.label2.Margin = new System.Windows.Forms.Padding(2, 0, 2, 0);
            this.label2.Name = "label2";
            this.label2.Size = new System.Drawing.Size(54, 20);
            this.label2.TabIndex = 9;
            this.label2.Text = "名称：";
            // 
            // label3
            // 
            this.label3.AutoSize = true;
            this.label3.Location = new System.Drawing.Point(456, 15);
            this.label3.Margin = new System.Windows.Forms.Padding(2, 0, 2, 0);
            this.label3.Name = "label3";
            this.label3.Size = new System.Drawing.Size(54, 20);
            this.label3.TabIndex = 10;
            this.label3.Text = "位置：";
            // 
            // btnQuery
            // 
            this.btnQuery.Location = new System.Drawing.Point(810, 13);
            this.btnQuery.Margin = new System.Windows.Forms.Padding(2, 4, 2, 4);
            this.btnQuery.Name = "btnQuery";
            this.btnQuery.Size = new System.Drawing.Size(96, 31);
            this.btnQuery.TabIndex = 11;
            this.btnQuery.Text = "查询";
            this.btnQuery.UseVisualStyleBackColor = true;
            this.btnQuery.Click += new System.EventHandler(this.btnQuery_Click);
            // 
            // txtNum
            // 
            this.txtNum.Location = new System.Drawing.Point(85, 13);
            this.txtNum.Name = "txtNum";
            this.txtNum.Size = new System.Drawing.Size(100, 27);
            this.txtNum.TabIndex = 12;
            // 
            // txtName
            // 
            this.txtName.Location = new System.Drawing.Point(277, 13);
            this.txtName.Name = "txtName";
            this.txtName.Size = new System.Drawing.Size(152, 27);
            this.txtName.TabIndex = 13;
            // 
            // txtLocation
            // 
            this.txtLocation.Location = new System.Drawing.Point(526, 13);
            this.txtLocation.Name = "txtLocation";
            this.txtLocation.Size = new System.Drawing.Size(170, 27);
            this.txtLocation.TabIndex = 14;
            // 
            // LandDataForm
            // 
            this.AutoScaleDimensions = new System.Drawing.SizeF(120F, 120F);
            this.AutoScaleMode = System.Windows.Forms.AutoScaleMode.Dpi;
            this.ClientSize = new System.Drawing.Size(928, 540);
            this.Controls.Add(this.txtLocation);
            this.Controls.Add(this.txtName);
            this.Controls.Add(this.txtNum);
            this.Controls.Add(this.btnQuery);
            this.Controls.Add(this.label3);
            this.Controls.Add(this.label2);
            this.Controls.Add(this.dataGridView1);
            this.Controls.Add(this.btn_Cancel);
            this.Controls.Add(this.btn_Ok);
            this.Controls.Add(this.label1);
            this.Cursor = System.Windows.Forms.Cursors.Hand;
            this.Font = new System.Drawing.Font("微软雅黑", 9F, System.Drawing.FontStyle.Regular, System.Drawing.GraphicsUnit.Point);
            this.FormBorderStyle = System.Windows.Forms.FormBorderStyle.FixedSingle;
            this.Margin = new System.Windows.Forms.Padding(2, 4, 2, 4);
            this.MaximizeBox = false;
            this.MinimizeBox = false;
            this.Name = "LandDataForm";
            this.StartPosition = System.Windows.Forms.FormStartPosition.CenterScreen;
            this.Text = "数据查询";
            this.FormClosing += new System.Windows.Forms.FormClosingEventHandler(this.ImportExcelFile_FormClosing);
            this.Load += new System.EventHandler(this.ImportExcelFile_Load);
            ((System.ComponentModel.ISupportInitialize)(this.dataGridView1)).EndInit();
            this.ResumeLayout(false);
            this.PerformLayout();

        }

        #endregion

        private System.Windows.Forms.Label label1;
        private System.Windows.Forms.Button btn_Ok;
        private System.Windows.Forms.Button btn_Cancel;
        private System.Windows.Forms.OpenFileDialog openFileDialog1;
        private System.Windows.Forms.DataGridView dataGridView1;
        private System.Windows.Forms.Label label2;
        private System.Windows.Forms.Label label3;
        private System.Windows.Forms.Button btnQuery;
        private System.Windows.Forms.TextBox txtNum;
        private System.Windows.Forms.TextBox txtName;
        private System.Windows.Forms.TextBox txtLocation;
        private System.Windows.Forms.DataGridViewTextBoxColumn Column1;
        private System.Windows.Forms.DataGridViewTextBoxColumn Column4;
        private System.Windows.Forms.DataGridViewTextBoxColumn Column2;
        private System.Windows.Forms.DataGridViewTextBoxColumn Column3;
    }
}

using System;
using System.Collections.Generic;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Threading;
using System.Threading.Tasks;
using System.Windows.Forms;
using WinFormsApp1.Class;

namespace WinFormsApp1
{
    public partial class LandDataForm : Form
    {
        //获取系统缩放比
        public static List<LandData> selectDate;
        List<LandData> LandDataAllList = new List<LandData>();
        public LandDataForm()
        {
            InitializeComponent();
        }

        private void btnQuery_Click(object sender, EventArgs e)
        {
            #region 
            string num = txtNum.Text == null ? string.Empty : txtNum.Text.Trim();
            string name = txtName.Text == null ? string.Empty : txtName.Text.Trim();
            string location = txtLocation.Text == null ? string.Empty : txtLocation.Text.Trim();
            //声明查询参数
            Func<LandData, bool> filterNum = x => true, filterName = x => true, filterLocation = x => true;
            //设置查询条件
            filterNum = x => x.num == num;
            filterName = x => x.name == name;
            filterLocation = x => x.location.Contains(location);//模糊查询

            var result = LandDataAllList;
            //查询
            if (!string.IsNullOrEmpty(num))
            {
                result = result.Where(filterNum).ToList();
            }
            if (!string.IsNullOrEmpty(name))
            {
                result = result.Where(filterName).ToList();
            }
            if (!string.IsNullOrEmpty(location))
            {
                result = result.Where(filterLocation).ToList();
            }
            dataGridView1.DataSource = result;

            if (result.Count > 0)
            {
                MessageBox.Show("查询结果成功");
            }
            else
            {
                MessageBox.Show("查询结果为空");
            }
            #endregion

        }

        private void btn_Ok_Click(object sender, EventArgs e)
        {
            
        }

        private void btn_Cancel_Click(object sender, EventArgs e)
        {
            this.DialogResult = DialogResult.Cancel;
            this.Close();
        }

        private void ImportExcelFile_FormClosing(object sender, FormClosingEventArgs e)
        {
        }
        private void ImportExcelFile_Load(object sender, EventArgs e)
        {
            Color rblue = ColorTranslator.FromHtml("#3A80EC");
            btn_Ok.FlatStyle = FlatStyle.Flat;
            btn_Ok.BackColor = rblue;
            btn_Ok.FlatAppearance.BorderColor = rblue;
            btn_Ok.ForeColor = Color.White;

            btn_Cancel.FlatStyle = FlatStyle.Flat;
            btn_Cancel.ForeColor = rblue;
            btn_Cancel.FlatAppearance.BorderColor = rblue;

            for (int i = 0; i < 30; i++)
            {
                LandDataAllList.Add(new LandData("num" + i, "name" + i, "位置" + i));
            }

            btnQuery_Click(null, null);

        }

        private void dataGridView1_RowPostPaint(object sender, DataGridViewRowPostPaintEventArgs e)
        {
            foreach (DataGridViewRow row in dataGridView1.Rows)
            {
                row.Cells[0].Value = row.Index + 1;
            }
        }
    }
}

<root>
  <xsd:schema id="root" xmlns="" xmlns:xsd="http://www.w3.org/2001/XMLSchema" xmlns:msdata="urn:schemas-microsoft-com:xml-msdata">
    <xsd:import namespace="http://www.w3.org/XML/1998/namespace" />
    <xsd:element name="root" msdata:IsDataSet="true">
      <xsd:complexType>
        <xsd:choice maxOccurs="unbounded">
          <xsd:element name="metadata">
            <xsd:complexType>
              <xsd:sequence>
                <xsd:element name="value" type="xsd:string" minOccurs="0" />
              </xsd:sequence>
              <xsd:attribute name="name" use="required" type="xsd:string" />
              <xsd:attribute name="type" type="xsd:string" />
              <xsd:attribute name="mimetype" type="xsd:string" />
              <xsd:attribute ref="xml:space" />
            </xsd:complexType>
          </xsd:element>
          <xsd:element name="assembly">
            <xsd:complexType>
              <xsd:attribute name="alias" type="xsd:string" />
              <xsd:attribute name="name" type="xsd:string" />
            </xsd:complexType>
          </xsd:element>
          <xsd:element name="data">
            <xsd:complexType>
              <xsd:sequence>
                <xsd:element name="value" type="xsd:string" minOccurs="0" msdata:Ordinal="1" />
                <xsd:element name="comment" type="xsd:string" minOccurs="0" msdata:Ordinal="2" />
              </xsd:sequence>
              <xsd:attribute name="name" type="xsd:string" use="required" msdata:Ordinal="1" />
              <xsd:attribute name="type" type="xsd:string" msdata:Ordinal="3" />
              <xsd:attribute name="mimetype" type="xsd:string" msdata:Ordinal="4" />
              <xsd:attribute ref="xml:space" />
            </xsd:complexType>
          </xsd:element>
          <xsd:element name="resheader">
            <xsd:complexType>
              <xsd:sequence>
                <xsd:element name="value" type="xsd:string" minOccurs="0" msdata:Ordinal="1" />
              </xsd:sequence>
              <xsd:attribute name="name" type="xsd:string" use="required" />
            </xsd:complexType>
          </xsd:element>
        </xsd:choice>
      </xsd:complexType>
    </xsd:element>
  </xsd:schema>
  <resheader name="resmimetype">
    <value>text/microsoft-resx</value>
  </resheader>
  <resheader name="version">
    <value>2.0</value>
  </resheader>
  <resheader name="reader">
    <value>System.Resources.ResXResourceReader, System.Windows.Forms, Version=5.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089</value>
  </resheader>
  <resheader name="writer">
    <value>System.Resources.ResXResourceWriter, System.Windows.Forms, Version=5.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089</value>
  </resheader>
  <metadata name="openFileDialog1.TrayLocation" type="System.Drawing.Point, System.Drawing, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a">
    <value>17, 17</value>
  </metadata>
  <metadata name="Column1.UserAddedColumn" type="System.Boolean, mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089">
    <value>True</value>
  </metadata>
  <metadata name="Column4.UserAddedColumn" type="System.Boolean, mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089">
    <value>True</value>
  </metadata>
  <metadata name="Column2.UserAddedColumn" type="System.Boolean, mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089">
    <value>True</value>
  </metadata>
  <metadata name="Column3.UserAddedColumn" type="System.Boolean, mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089">
    <value>True</value>
  </metadata>
</root>