无法在搜索中显示 gridview 数据

Question

加载页面时，我能够从数据库中检索数据，显示到目前为止数据库中的所有数据。但是当我打算使用文本框和搜索按钮时，我收到一条错误消息 "ERROR: MUST DECLARE THE SCALAR VARIABLE @MRF_NO"。我的代码有问题吗？？我会post代码。

C#

private void searchsumm()
    {
        database db = new database();
        string database = db.MRF();
        using (SqlConnection con = new SqlConnection(database))
        {
            con.Open();

            string query = "Select MRF_No, BU, Dept,ReqByDept_Mngr FROM MRF_Details";
            using (SqlCommand com = new SqlCommand(query, con))

            if (!string.IsNullOrEmpty(txtSearch.Text.Trim()))
            {
                query += " WHERE ContactName LIKE @MRF_No + '%'";
                com.Parameters.AddWithValue("@MRF_No", txtSearch.Text.Trim());
            }

            using (SqlDataAdapter sda = new SqlDataAdapter(query, con))
            {
                DataTable dt = new DataTable();
                sda.Fill(dt); //Error: Must declare the scalar variable "@MRF_No".
                smry.DataSource = dt;
                smry.DataBind();
            }
            con.Close();
        }

    }

ASP.NET

<div class="col-sm-4">
                <asp:TextBox ID="txtSearch" runat="server" ReadOnly="false" CssClass="form-control"></asp:TextBox>  
            </div>

            <div class="col-sm-5">
                <asp:Button ID="searchdb" runat="server" CssClass="btn" Text="Search" onclick="btnsummary"/>
            </div>

            <div class="row-space"></div>

        <asp:GridView runat="server" ID="smry" CssClass="list-group" AutoGenerateColumns="False" AllowPaging="true"  >

            <Columns>
                <asp:BoundField DataField="MRF_No" HeaderText="MRF No" SortExpression="MRF_No" />
                <asp:BoundField DataField="BU" HeaderText="Business Unit" SortExpression="BU" />
                <asp:BoundField DataField="Dept" HeaderText="Department" SortExpression="Dept" />
                <asp:BoundField DataField="ReqByDept_Mngr" HeaderText="Request By" SortExpression="ReqByDept_Mngr" />
            </Columns>

        </asp:GridView>

Answer 1

您的查询似乎在 where 子句中有误：

query += " WHERE ContactName LIKE @MRF_No + '%'";

应该是：

query += " WHERE ContactName LIKE '%' + @MRF_No + '%'";

此外，我认为您需要创建 SqlDataAdapter 并传递您刚刚构建的命令，以便查询包含您定义的参数。

using (SqlDataAdapter sda = new SqlDataAdapter(com))
{
     DataTable dt = new DataTable();
     sda.Fill(dt);
     smry.DataSource = dt;
     smry.DataBind();
}

Answer 2

可能是语法问题。你能看看下面是否有效：

query += " WHERE ContactName LIKE @MRF_No";
com.Parameters.AddWithValue("@MRF_No", "%" + txtSearch.Text.Trim() + "%");

无法在搜索中显示 gridview 数据

Unable to display gridview data on search

c#

asp.net

gridview