c# - 查询中的“条件是预期的”

Question

SqlConnection conn = new SqlConnection("Data Source=.\\SQLEXPRESS;AttachDbFilename=D:\\Projects\\csharp\\Login1\\App_Data\\Login.mdf;Integrated Security=True;User Instance=True");
SqlCommand cmd;
SqlDataReader dr;   

protected void  LinkButton1_Click(object sender, EventArgs e)
{
 conn.Open();
 cmd=new SqlCommand("Select * from LoginTable where User Name='"+TextBox1.Text+"'",conn);
 dr=cmd.ExecuteReader();   //  <---error here

 if(dr.Read())
 {
   Label1.Text="User name already exist";
   this.Label1.ForeColor=Color.Red;
 }
 else
 {
   Label1.Text="Name available";
 }
}

它在 dr=cmd.ExecuteReader(); 附近显示以下错误:

An expression of non-boolean type specified in a context where a condition is expected, near 'Name'.

这里发生了什么

Answer 1

将where子句中的User Name替换为[User Name]