如何从Database列获取值到变量 [英] How to get value from column of Database to variable

问题描述

我的数据库有3列是名称，数学，化学和总和。我可以在C＃中通过SQL查询某些行，但我不知道如何在C＃中将值从列变为变量。如果有人知道，请帮助我！



例如：

 SqlConnection con; 
 SqlCommand cm1; 
 DataSet ds; 
 SqlDataAdapter ap; 
 
  private   void  btn_info_Click（对象 sender，EventArgs e）
 {
 cm1 =  new  SqlCommand（  SELECT * FROM Database，con）; 
 
 ap =  new  SqlDataAdapter（cm1）; 
 ds =  new  System.Data.DataSet（）; 
 ap.Fill（ds， 数据库）; 
 DataGridView1.DataSource = ds.Tables [ 0 ]; 
 DataGridView1.DisplayMember =   Math; 
} 

我的数据库有7行，因此Math列有7行值为{10,5.5,6,7.5,9,8,8.5}。

我使用查询SELECT * FROM Database。

之后，我怎样才能将Math列的值变为数组或变量？

解决方案

嗯，你已经拥有了它在一个集合中 - 你填充并用作DataGridView的数据源的DataTable - 所以我可能会从中访问这些值。

试试这个：

< pre lang =c＃> DataTable dt = ds.Tables [ 0 ];
double [] mathValues = new double [dt.Rows.Count];
int index = 0 ;
foreach （DataRow row in dt.Rows）
{
mathValues [index ++] =（ double ）row [ Math ];
}

  private   void  btn_info_Click（ object  sender，EventArgs e）
 
 SqlConnection con; 
 SqlCommand cm1; 
 DataSet ds; 
 SqlDataAdapter ap; 
 {
 cm1 =  new  SqlCommand（  SELECT * FROM Database，con）; 
 
 ap =  new  SqlDataAdapter（cm1）; 
 ap.Fill（ds）; 
 DataGridView1.DataSource = ds; 
 DataGridView1.DataBind（）; 
} 

My Database has 3 column are "Name", "Math", "Chemistry" and "Sum". I can query some rows by SQL in C#, but I don't know how to get the value from column to variable in C#. If anyone know, please help me!

For ex:

SqlConnection con;
SqlCommand cm1;
DataSet ds;
SqlDataAdapter ap;

private void btn_info_Click(object sender, EventArgs e)
{
    cm1 = new SqlCommand("SELECT * FROM Database ", con);

    ap = new SqlDataAdapter(cm1);
    ds = new System.Data.DataSet();
    ap.Fill(ds, "Database");
    DataGridView1.DataSource = ds.Tables[0];
    DataGridView1.DisplayMember = "Math";
}

My Database has 7 rows, so that column "Math" has 7 values are {10, 5.5, 6, 7.5, 9, 8, 8.5}.
I use the query "SELECT * FROM Database".
After that, How can I get the value of Math column to an array or a variable?

解决方案

Well, you already have it in a collection - the DataTable that you filled and used as the data source for the DataGridView - so I'd probably access the values from that.
Try this:

DataTable dt = ds.Tables[0];
double[] mathValues = new double[dt.Rows.Count];
int index = 0;
foreach (DataRow row in dt.Rows)
   {
   mathValues[index++] = (double) row["Math"];
   }

private void btn_info_Click(object sender, EventArgs e)
   
SqlConnection con;
SqlCommand cm1;
DataSet ds;
SqlDataAdapter ap;
 {
        cm1 = new SqlCommand("SELECT * FROM Database ", con);

        ap = new SqlDataAdapter(cm1);
        ap.Fill(ds);
        DataGridView1.DataSource = ds;
        DataGridView1.DataBind();
    }

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